Yearly influenza epidemics affect about 5 - 15% of the world's population and estimates of annual mortality range from 250,000 - 500,000, including approximately 30,000 deaths and 200,000 hospitalizations in the United States. In addition, the likelihood of a severe influenza pandemic caused by a newly emergent strain of the virus is very high, given that three such pandemics were recorded in the 20th century. The most devastating of these, the 1918 Spanish Flu, was responsible for an estimated 40 million deaths worldwide. The annual vaccine for seasonal influenza is only partially effective in prevention of the disease. Likewise, currently available anti-influenza drugs such as amantadine and oseltamavir are only partially effective in treatment and also suffer from problems of viral resistance. Therefore there is an urgent need for additional anti-influenza therapeutics that attack unexploited aspects of viral biology. The proposed research is directed at developing new drugs that can combat influenza virus. The NS1 protein of influenza virus is an attractive drug target because it is essential for virus replication in vivo. Therefore drugs that inhibit NS1 function are expected to block virus replication, and hence disease. Several compounds that specifically inhibit NS1 function during infection have been identified. These compounds, which represent starting points for further drug development, also inhibit virus replication in cell culture. The goals of this proposal are to perform structure-activity and feasibility studies to determine how the first-generation compounds can be chemically modified to increase their potency while at the same time limiting their cellular toxicity. In Aim 1, medicinal chemistry approaches will be used to make initial sets of chemical derivatives. The design of these compounds will probe the chemical space around the backbone structures defined by the prototype active compounds. In Specific Aim 2, the derivatives will be tested using a set of biological assays that depend on the function of the NS1 protein. These include virus replication, induction of interferon mRNA, and physical binding to several cellular components including dsRNA and specific cellular proteins. The endpoint of these studies will be the identification of potent lead compounds for future development and animal testing. PUBLIC HEALTH RELEVANCE: Yearly influenza epidemics affect about 5 - 15% of the world's population and estimates of annual mortality range from 250,000 - 500,000, including approximately 30,000 deaths and 200,000 hospitalizations in the United States. The proposed research is directed at developing new drugs that can combat the influenza virus, the virus that causes influenza.